1. Field of the Invention
The present invention relates to the field of data processing, and in particular, to the prevention of unauthorized duplication of digital information on one storage medium to another. Furthermore, the present invention restricts the use of information on an original medium to one or more designated devices without introducing any key which is independent of the characteristics of the media.
2. Description of the Related Art
Prior art copy protection schemes rely principally on either software based methods, hardware keys or a combination thereof. Software based methods use encryption techniques to prevent conventional copying programs from making unauthorized usable copies. Unless the appropriate decryption key is found on a storage medium, the programs on the storage medium cease to function. By storage medium, the present invention refers to all types of non-volatile storage medium. Examples of such media include floppy disks, hard disks, optical disks and other non-volatile semiconductor storage devices. Lately, new generation of copying programs are sufficiently sophisticated such that most software previously protected by copy protection schemes are copied without the authorization of the information provider.
Hardware key methods employ an explicit key on the system hardware to enable the programs in the system. One such method uses as key the hardware serial number or identification number. A second method requires the user to buy a special kind of hardware with every purchase of software. Thus whenever a new software is required, the necessary hardware has to be plugged into the system hardware. As such, the number of concurrent software that can be run on a particular system is limited by the number of such special hardware that can be simultaneously connected to the system hardware.
An example of a combination of software based method and hardware key is U.S. Pat. No. 4,903,296 which claims copy protection of software on magnetic medium with a special key having two marks made on the surface of the medium. These marks are not producible by conventional disk drives and are in the form of absence of material and in the form of domains which cannot be formed by conventional magnetic disk write heads. Additionally, an encrypted key which is critical for running the application is built into a special purpose hardware subsystem. Finally the hardware subsystem is required to decrypt the key.
Another patent is U.S. Pat. No. 4,866,769 which claims a method of copy protection of personal computer software distributed in diskettes through the use of an unique identification stored in read only memory of a personal computer. A source ID is provided with every software distributed. The personal computer ID is used with the source ID on the distribution diskette to produce an encoded check word, using any available encryption method. This check word is then used to verify that the software is being used on the designated personal computer.
To prevent unauthorized copying and use of information, prior art copy protection schemes require either introducing artificial indica as software keys or requiring special hardware subsystems. Not only are these solutions more costly to both the information providers and the users as they require additional processing steps but they are also incompatible with the trend of encouraging concurrent use of different types of information in a network environment. Furthermore, the prior art copy protection schemes are restrictive in that they prevent unauthorized copying and use of only software in magnetic medium.